1. Field of the Invention
The present invention relates to an interchangeable lens which is detachably attached to a camera body and capable of performing data communications with the camera body. The present invention also relates to a lens data communication method between an interchangeable lens and a camera body of a camera system.
2. Description of the Related Art
A conventional camera system is used by combining a camera body and an interchangeable lens selected from among various interchangeable lenses, and accordingly, each interchangeable lens incorporates a memory into which lens data inherent in the interchangeable lens is written so that the camera body reads out this lens data from the memory to use this lens data for controlling a photographic operation at a time of exposure. For instance, in conventional zoom lenses such as disclosed in U.S. Pat. No. 6,336,754 and Japanese Unexamined Patent Publication H11-231398, lens data is written into memory by a paging method for each focal length step because the lens data needs to be changed according to variations in focal length caused by a zooming operation. Upon the focal length of the zoom lens being changed, a page corresponding to the changed focal length is detected and designated by a zoom-code output device and a distance-code output device, and thereupon the camera body reads in all the data in this designated page.
However, in conventional a SLR camera system, the camera body needs to send a readout command of 1 byte and a data address of 2 bytes to the interchangeable lens when reading lens data in from the interchangeable lens; hence, it takes an additional period of time of 3 bytes for the transmission of the lens data from the interchangeable lens to the camera body.